1. Field of the Invention
The present invention relates to an optical transceiver cage, and more particularly to a small form-factor pluggable (SFP) transceiver cage of a high data transfer rate program gigabit interface converter (GBIC).
2. Description of the Related Art
Transceiver modules provide bi-directional transmission of data between an electrical interface and an optical data link. The module receives electrically encoded data signals and converts them into optical signals, which are then transmitted over the optical data link. The module also receives optically encoded data signals, converts them into electrical signals, and transmits the electrical signals to the electrical interface.
Normally, the transceiver module is mounted on a printed circuit board (PCB) assembly of a host computer, an input/output system, a peripheral device, or a switch. An SFP transceiver module is inserted into a complementary metal cage assembly mounted on the PCB. The metal cage generally has two parallel sidewalls, a rectangular top, a rectangular bottom, and front and rear ends. The metal cage provides easy interconnection, and is easily installed on the PCB. The metal cage functions to dissipate electrostatic buildup, and serves as an electromagnetic shield.
A conventional cage has an entrance portion that is mounted in an opening of an orthogonal panel. A plurality of outwardly projecting grounding tabs adjacent the entrance portion of the cage abuts against edges of the panel that bound the opening. The cage further includes a spring latch at the entrance portion for engaging an SFP transceiver module, and spring arms at a rear portion of the cage for resiliently ejecting the transceiver module. The spring latch is partially received in the opening of the panel. A gap exists between the spring latch and an edge of the panel that bounds the opening. In use, electromagnetic interference (EMI) passes through the gap. The cage does not provide adequate protection for the connecting interface from EMI. In addition, the resilient force exerted by the spring arms on the SFP transceiver module is generally weak. As a result, the SFP transceiver module is liable to be accidentally released from engagement with the cage when the cage is subjected to vibration during normal operation.
Furthermore, there are no structures specifically for establishing grounding of a housing of the SFP transceiver module that is engaged in the cage. Moreover, the cage forms legs for supporting the cage on the PCB, but there is no board locking mechanism to safeguard reflowing of solder during soldering of the cage to the PCB. The cage is liable to disengage from the PCB, causing poor soldering.
Accordingly, an object of the present invention is to provide an SFP transceiver cage that gives excellent protection from EMI when the cage is mounted to a panel.
Another object of the present invention is to provide an SFP transceiver cage which prevents an inserted SFP transceiver from being accidentally released from the cage even when subjected to vibration.
A further object of the present invention is to provide an SFP transceiver cage which has ample grounding structures to facilitate grounding and prevent EMI.
A still further object of the present invention is to provide an SFP transceiver cage having legs that enable the cage to be locked on a PCB during soldering of the cage to the PCB.
A yet still further object of the present invention is to provide a sturdy SFP transceiver cage that is easily and inexpensively made essentially from a single metal plate.
To achieve the above objects, an SFP transceiver cage in accordance with a preferred embodiment of the present invention comprises a mainframe and a rectangular grounding device mounted around a front portion of the mainframe. The mainframe includes two sidewalls, a sidewall cover, a top plate, a bottom wall and a rear cover. The mainframe and grounding device are each preferably made from a single piece of metal plate. A plurality of inward grounding fingers is formed on a top, bottom and sides of a front portion of the mainframe. A plurality of outward grounding fingers is formed on a top, bottom and sides of the grounding device, symmetrically opposite the inward grounding fingers of the mainframe. A central spring latch is formed at the bottom of the front portion of the mainframe, and two kick-out spring arms respectively extend inwardly from rear edges of the sidewalls.
A plurality of compliant legs, needle eye legs and support legs depends from the sidewalls of the mainframe. The compliant and needle eye legs are extended through corresponding holes defined in a PCB, and prevent the cage from moving relative to the PCB during the course of solder reflowing. The support legs abut a face of the PCB. The support legs serve as standoffs, separating the cage from the PCB to facilitate accurate soldering.
A front portion of the cage is mounted in an opening of an orthogonal panel, leaving a gap between the panel and the cage. The grounding device mounted around the front portion of the mainframe substantially fills the gap. The outward grounding fingers of the grounding device resiliently engage with edges of the panel that surround the opening. The central outward spring tab serves as an EMI shield for any EMI that may pass through a gap existing between the panel and a spring latch of the mainframe. An SFP transceiver module having a conductive outer surface is inserted into the cage, with a rear part of the SFP transceiver module abutting against the kick-out spring arms. The SFP transceiver module has a buckle engaged in a corresponding hole in the central outward spring latch of the cage. The kick-out spring arms of the mainframe are configured to resiliently and firmly secure the buckle of the SFP transceiver module in the hole in the central spring Latch. The inward grounding fingers of the mainframe resiliently engage with the conductive outer surface of the SFP transceiver module. The inward and outward grounding fingers and central outward spring tab cooperate to establish multiple grounding paths between the SFP transceiver module and the mainframe, grounding device and panel.